This invention is related generally to the field of Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), Near field Scanning Optical Microscopy (NSOM), NanoSpectroPhotometry (NSP), NanoPolarimetry (NP), Magnetic Field Microscopy (MFM) and any other methods adaptable and suitable to guide the nanomachining techniques described herein. Specifically, the invention is directed to scanning probes for use in AFM, NSOM, NSP, NP, MFM and STM technologies. These technologies are sometimes collectively referred to as Scanning Probe Microscopy (SPM). Generally, SPM technologies allow one to “see” atomic-scale features on or in surfaces.
An AFM works by scanning a tip over a surface much the same way as a phonograph needle scans a record. The tip is located at the end of a cantilever beam and positioned over the surface to be scanned. The combination of the cantilever beam and tip is sometimes referred to collectively as a scanning probe or simply a probe.
AFM techniques rely on the effects of the inter-atomic interactions, such as van der Waals forces, that arise between the atoms in the structure of the tip and the atoms at the surface being imaged. As the tip is repelled by or attracted to the surface, the cantilever beam is deflected. The magnitudes of the deflections correspond to the topological features of the atomic structure of the surface being scanned. The AFM can work with the tip touching the sample (contact mode), or the tip can tap across the surface (tapping mode).
STM techniques rely on the fact that the electron cloud associated with the atoms at the surface extends a very small distance above the surface. When a tip—in practice, a needle which has been treated so that a single atom projects from its end—is brought sufficiently close to such a surface, there is a strong interaction between the electron cloud on the surface and that of the tip atom. An electric tunneling current flows when a small voltage is applied. The tunneling current is very sensitive to the distance between the tip and the surface. These changes in the tunneling current with distance as the tip is scanned over the surface are used to produce an image of the surface.
AFM is being used to solve processing and materials problems in a wide range of technologies affecting the electronics, telecommunications, biological, chemical, automotive, aerospace, and energy industries. The materials being investigated include thin and thick film coatings, ceramics, composites, glasses, synthetic and biological membranes, metals, polymers, and semiconductors. The AFM is being applied to studies of phenomena such as abrasion, adhesion, cleaning, corrosion, etching, friction, lubrication, plating, and polishing.
The STM is widely used in both industrial and fundamental research to obtain atomic-scale images of surfaces. It can provide a three-dimensional profile of the surface which is very useful for characterizing surface roughness, observing surface defects, and determining the size and conformation of molecules and aggregates on the surface.
Different SPM tasks, such as metrology, mechanical transport, nanofabrication, nanomanipulation, and nanomachining operations and/or measurements, impose different requirements in the behavior of the SPM probe. Conventionally, different probes are used for different functions.